1. Field of the Invention
The present invention relates to optical recording media recordable on land and groove tracks, and more particularly, to an optical recording medium having an improved structure to compensate for defects of conventional land/groove optical recording media.
2. Description of the Related Art
DVD-RAM optical recording media use a land/groove recording method by which user data is written both on land and groove tracks. FIG. 1 illustrates a part of a conventional land/groove optical recording medium 1 capable of performing the above operation. DVD-RAM optical recording media, which are a type of the land/groove optical recording medium 1, are manufactured to have grooves of xcex/6 in depth to minimize cross talk between adjacent tracks. Here, xcex denotes the wavelength of an optical source that is used to record and/or reproduce DVD-RAM optical recording media.
The land/groove optical recording medium 1 has a track pitch about twice as long as the pitch of groove-only optical recording media that record user data only on grooves. Here, the track pitch denotes the distance between groove tracks Gxe2x80x2. Therefore, xc2x11st-order diffracted light beams, from light projected onto the land/groove optical recording medium 1 and diffracted by the land/groove structure, enter the inner side of the exit pupil of an objective lens, as compared to groove-only optical recording media. Accordingly, it is well known that the land/groove optical recording medium 1 can obtain a push-pull signal of sufficient magnitude. That is, the land/groove optical recording medium 1 can obtain a tracking error signal of sufficient magnitude.
As shown in FIG. 1, during manufacturing of the land/groove optical recording medium 1, a wobble signal is molded into the groove tracks Gxe2x80x2 and/or the land tracks Lxe2x80x2 using changes in the amplitude direction. The wobble signal is used to control the rotating speed of the optical recording medium 1 and to obtain synchronization information of the optical recording medium 1. In the land/groove optical recording medium 1, user data is recorded both on the land tracks Lxe2x80x2 and on the groove tracks Gxe2x80x2. The frequency-modulated or phase-modulated wobble is simply formed into both sidewalls of each of the groove tracks Gxe2x80x2. Thus, it is impossible to record address information to recognize physical locations on the optical recording medium 1.
In order to record address information, as shown in FIG. 2, the optical recording medium 1 such as a DVD-RAM has rugged pre-pits 3 formed on its header area using a complementary allocated pit address (CAPA) method. A track pitch is less than the size of a light spot. Thus, as shown in FIG. 2, the CAPA method forms pre-pits in the header area on the border of adjacent tracks at intervals of two tracks in order to minimize the influence upon the pre-pits of adjacent tracks. Here, a wobble signal and an address signal can be obtained from a push-pull signal, which is obtained by performing a differential operation on detected signals. The detected signals are obtained by dividing the light beams reflected/diffracted by the land/groove optical recording medium 1 into two parts in the radial direction of the optical recording medium 1, and by detecting electrical signals from the two reflected/diffracted light beam parts.
However, as described above with respect to the DVD-RAM optical recording medium as an example, the conventional land/groove optical recording medium 1 generally has the pre-pits 3 formed in the header area to record address information. Therefore, the recording density is reduced by the pre-pit area formed to record the address information. In addition, the grooves and the pre-pits are mixed up on the conventional land/groove optical recording medium 1 such that the light amount from the light beams reflected by the optical recording medium varies depending on the positions on the optical recording medium 1 irradiated by the light beam. Thus, it is impossible to achieve multi-layered recording.
To solve the above and other problems, it is an object of the present invention to provide an optical recording medium having an improved structure such that a recordable area (user data area) can be increased by a reduction of a non-recordable area (overhead).
To solve the above and other problems, it is another object of the present invention to provide an optical recording medium having an improved structure to have the merits of conventional land/groove optical recording media and those of groove-only optical recording media, and which uses a wobble addressing technique to record a wobble signal with address information.
Additional objects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
In order to achieve the above and other objects of the present invention, an optical recording medium having groove tracks and land tracks according to an embodiment of the invention includes a first wobble formed close to a groove track along both sidewalls of a groove track and a second wobble formed close to a land track along both sidewalls of a land track independently of the formation of the first wobble.
According to an aspect of the invention, the optical recording medium further includes a middle portion formed at a predetermined position on the sidewall between adjacent land and groove tracks, the middle portion to divide the area where the first wobble is formed and the area where the second wobble is formed.
In order to achieve the above and other objects of the present invention, an optical recording medium having groove tracks and land tracks according to another embodiment includes a middle portion formed at a predetermined position on the sidewall between adjacent land and groove tracks.
According to another aspect of the invention, the optical recording medium further includes a first wobble formed on the sidewall between a groove track and the adjacent middle portion, and a second wobble formed on the sidewall between a land track and the adjacent middle portion.
According to a further aspect of the invention, wobble signals carrying address information are recorded on the first and second wobbles.
According to a still further aspect of the invention, bi-phase-modulated wobble signals, frequency-modulated wobble signals and/or amplitude-modulated wobble signals are recorded on the first and second wobbles.
According to a yet further aspect of the invention, the address information recorded on the first wobble is detected during groove track scanning and the address information recorded on the second wobble is detected during land track scanning.